Outer casing for control cable, method of manufacturing the same, and control cable

ABSTRACT

An outer casing for a control cable  10  has an inner tube  12, which includes a crystalline resin, and an outer tube  14,  which includes an outer resin layer  16  covering the outer periphery of the inner tube and, in the outer resin layer, includes plural metal wires  18  buried in parallel with the axial direction of the inner tube and at equal intervals in the circumferential direction of the inner tube.

TECHNICAL FIELD

The present invention relates to an outer casing for a control cableused in vehicles or the like and a method of manufacturing the same, andfurther relates to a control cable.

BACKGROUND ART

A typical control cable is formed by a flexible pipe-shaped outer casingand an inner cable made of a metal wire, with the inner cable beinginserted through the outer casing. The control cable has a remotecontrol function by pushing, pulling, or rotating one end of the controlcable to realize remote control of a passive type device disposed at theother end of the control cable. For example, the control cable may beused in a vehicle for various purposes, such as an open/close cable fora sunroof, an open/close cable for windows, or a cable for the parkingbreak.

For an outer casing of the control cable, dimensional stability in alongitudinal direction is strictly required. Since the inner cable is ametal wire, a linear expansion coefficient and a compressioncharacteristic equivalent to those of the metal wire are required.

If thermal expansion of the outer casing is large, the inner cable actsas if pulled even when the inner cable is not operated. This may cause amalfunction such as failure to close an oil supply port. If the outercasing is soft, the length of the outer casing may be compressed andshortened by operation of the inner cable. In such a case, the controlcable may be inoperable even when the inner cable is pulled.

Such things can be confirmed by measuring a thermal expansion and strokeloss (play of the inner cable that causes malfunction if it is toolarge) of resin of the outer casing. Specifically, stroke loss ismeasured by measuring stroke values relative to a load acted on theinner cable by changing temperatures. A lower value of stroke loss ispreferable.

The outer casing made of resin tends to generate problems as describedabove. A tubular body, therefore, that is formed by tightly winding aflat steel wire around the outer periphery of an inner tube (liner) madeof resin in a spiral manner, with the outer side of the tubular bodyfurther covered by resin has conventionally been used (see JapanesePatent Application Laid-Open No. 2002-286017, for example).

However, such an outer casing around which the flat steel wire isspirally and tightly wound is heavy, and does not satisfy lightweightrequirement in the recent trend of electric vehicles or hybrid vehicles.

Meanwhile, an outer casing in which a metal wire is linearly buried in aresin layer has been proposed (see JP-A Nos. S47-11410, S59-16726, and2011-99524, and Japanese Utility Model Application Laid-Open No.59-22322, for example).

For example, an outer casing for a control cable in which a reinforcingwire, in which flat portions are formed by pressing a metal tube atappropriate intervals, is buried in parallel with an axial center of thecasing body in the thickness of the tubular casing body made ofsynthetic resin has been proposed (see JP-U No. S59-22322).

A method of manufacturing an outer casing by introducing a metal wireinto an extruder and burying the metal wire in a thickness part of thetubular conduit made of resin has also been proposed (see JP-A No.S59-16726, for example).

A control cable used in a drain plug remote operation apparatus, whichhas an outer casing including two metal wires buried in a cylindricalbody made of polyolefin-based thermoplastic elastomer in parallel withthe axis of the body and opposing from each other by 180 degrees aboutthe axis has also been proposed (see JP-A 2011-99524).

SUMMARY OF INVENTION Technical Problem

When it is desired to produce an outer casing with a metal wire linearlyburied in a thickness part of a tubular body made of resin, the metalwire is introduced into the die of an extruder to extrude the resin in atubular shape, and the obtained tubular body is passed through an outerdiameter adjusting apparatus (former) in which a vacuum apparatus isprovided to adjust inner and outer diameters. However, such adjustmentis difficult and takes a long time, and increases the amount of wastematerials.

The resin to be used is limited to a rigid resin, such as polypropylene.Other resins, such as a soft thermoplastic elastomer and soft vinylchloride are difficult to be controlled, because such resins may bulgein the vacuum apparatus during adjustment of the outer diameter.

It is an object of the invention to provide an outer casing for acontrol cable which has a low thermal expansion, is lightweight, and canbe manufactured easily, a method of manufacturing such an outer casing,and a control cable.

Solution to Problem

To achieve the above object, the invention is provided as describedbelow.

A first aspect of the invention is an outer casing for a control cable,the outer casing including an inner tube, which includes a crystallineresin, and an outer tube, which includes an outer resin layer coveringan outer periphery of the inner tube and, in the outer resin layer,includes a plurality of metal wires buried in parallel with an axialdirection of the inner tube and at equal intervals in a circumferentialdirection of the inner tube.

A second aspect of the present invention is the outer casing for acontrol cable according to the first aspect, in which the crystallineresin included in the inner tube has a melting point of 120° C. orhigher.

A third aspect of the invention is the outer casing for a control cableaccording to the first or second aspect, in which a resin included inthe outer resin layer is a thermoplastic elastomer or soft vinylchloride.

A fourth aspect of the invention is the outer casing for a control cableaccording to any one of the first to third aspects, in which at leastone of a contact surface between the inner tube and the outer resinlayer or a contact surface between the metal wires and the outer resinlayer has been subjected to easy adhesion treatment.

A fifth aspect of the invention is a method of manufacturing an outercasing for a control cable, the method including a step of forming anouter tube including an outer resin layer and a plurality of metal wiresburied in the outer resin layer by inserting, into a die of an extrusionforming machine, an inner tube including a crystalline resin inserting,together with the plurality of metal wires in parallel with an axialdirection of the inner tube and at equal intervals in a circumferentialdirection of the inner tube, and extruding a resin around an outerperiphery of the inner tube while feeding out the inner tube and theplurality of metal wires from the die.

A sixth aspect of the present invention is a control cable including theouter casing for a control cable according to any one of the first tofourth aspects, and an inner cable inserted into the outer casing for acontrol cable.

Advantageous Effects of Invention

According to the first aspect of the invention, an outer casing for acontrol cable, which is easy to route, has low thermal expansion, islightweight, and is easy to produce, is provided.

According to the second aspect of the invention, an outer casing for acontrol cable having yet further increased slidability relative to theinner cable is provided.

According to the third aspect of the invention, an outer casing for acontrol cable capable of further improving routing properties isprovided.

According to the fourth aspect of the invention, an outer casing for acontrol cable capable of restricting slipping movement between membersand increasing anti-compression force to further decrease stroke loss,is provided.

According to the fifth aspect of the invention, a method ofmanufacturing an outer casing for a control cable, capable of easilymanufacturing an outer casing for a control cable, which is easy toroute, has low thermal compression, and is lightweight, is provided.

According to the six aspect of the invention, a control cable that iseasy to route, has low thermal expansion, and is lightweight, isprovided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view showing an exemplary structure of an outercasing for a control cable of the invention.

FIG. 2 is a schematic view showing another exemplary structure of anouter casing for a control cable of the invention.

FIG. 3 is a schematic view showing a step to form an outer tube aroundan outer periphery of an inner tube when an outer casing for a controlcable is manufactured.

FIG. 4 is a schematic view for explaining how stroke loss is measured.

FIG. 5 is a schematic view for explaining how load efficiency ismeasured.

DESCRIPTION OF EMBODIMENTS

An outer casing for a control cable (which may simply be referred to asan “outer casing” hereinafter) and a control cable according to theinvention will be described in detail below by referring to theaccompanying drawings.

<Outer Casing for Control Cable>

An outer casing for a control cable of the invention includes an innertube, which includes a crystalline resin, and an outer tube, whichincludes an outer resin layer covering the outer periphery of the innertube and, in outer resin layer, includes plural metal wires buried inparallel with the axial direction of the inner tube and at equalintervals in the circumferential direction of the inner tube.

The outer casing of the present invention has a two-layered structure inwhich the outer tube the inner tube (liner) made of the crystallineresin is inserted into the inside of the outer tube including the pluralmetal wires buried in parallel with the axial direction and at equalintervals in the circumferential direction in the outer resin layer.With such a structure, extrusion molding can be executed with very highproductivity, and measurements of inner and outer diameters can beprovided at high accuracy.

In addition, routing is easy for such an outer casing having the abovestructure, because the outer casing exhibits an excellent dimensionalaccuracy even when a soft resin is used for the outer resin layer. Bothslidability and routing properties, which cannot be realized in asingle-layer outer casing, can therefore be realized.

The outer casing of the invention is configured as a combination of theinner tube made of the crystalline resin and the outer tube with pluralmetal wires linearly buried in the outer resin layer. Therefore, theouter casing is lightweight, easy to route, and is difficult tothermally expand at a wide range of temperatures and has a favorablecompression resistance, and thus has low stroke loss. The outer casingof the invention is largely lightweight, having more excellentperformance, and can be produced more easily, compared to a conventionalouter casing formed by tightly winding a flat steel wire or a roundsteel wire around the inner resin tube spirally and covering the outsideof the inner resin tube with resin.

Namely, the outer casing of the invention satisfies requirement ofperformances as the control cable in routing properties, stroke loss,and load efficiency. In addition, the outer casing of the invention iseasy to manufacture, and thus easy to keep a certain quality level.

FIG. 1 schematically shows an exemplary structure of the outer casingfor a control cable according to an embodiment of the invention. Anouter casing 10 according to the invention is formed by an inner tube 12including a crystalline resin and an outer tube 14 including an outerresin layer 16 covering the outer periphery of the inner tube 12 and twometal wires 18 buried in parallel with each other in the axial directionof the inner tube 12 and at equal intervals (at positions symmetricalabout the axis) in the circumferential direction of the inner tube 12 inthe outer resin layer 16. Constituent members will be describedhereinafter.

(Inner Tube)

An inner tube 12 (may be referred to as a “resin liner” or a “liner”hereinafter) includes the crystalline resin.

A melting point of the crystalline resin forming the liner 12 ispreferably in a range equal to or higher than 120° C. The liner 12formed with the crystalline resin having the melting point in this rangehas a high slidability relative to an inner cable (not shown). Inaddition, when the resin to form an outer resin layer 16 is extruded athigh temperature around the outer peripheral surface of the liner 12 tocover the liner 12 in manufacturing, the fusing or deforming of theliner 12 is restricted.

For example, even when a high density polyethylene which has arelatively low melting point (melting point of 135° C.) is used as thecrystalline resin, the liner 12 is hardly deformed during extrusionmolding of the outer resin layer 16. If a crystalline resin having ahigher melting point is used, deformation is further restricted.

An upper limit of the melting point of the crystalline resin forming theliner 12 is preferably about 265° C. Molding is easy if the meltingpoint is not more than 265° C., as the extrusion can be carried out at arelatively low temperature.

If the resin that forms the liner 12 is amorphous resin, even when avery hard resin, such as polycarbonate, is used, or grease is injectedin the inner peripheral surface of the liner, the slidability of theliner 12 relative to the inner cable is deteriorated and the function asa control cable is greatly decreased.

Examples of the crystalline resins to form the liner 12 include nylon 66(melting point of 260 degrees), nylon 6 (melting point of 220 degrees),polybutylene terephthalate (melting point of 220 degrees),polyoxymethylene (melting point of from 165 to 175 degrees),polymethylpentene (melting point of 230 degrees), polypropylene (meltingpoint of 165 degrees), and high density polyethylene (melting point of135 degrees). These resins are preferable because friction coefficientsare low and load efficiencies are high. In particular, a high loadefficiency is easily obtained by using polybutylene phthalate,polyoxymethylene, or high density polyethylene.

The thickness of the liner 12 is preferably from 50 to 1,000 μm, and isparticularly preferably from 100 to 500 μm, in order to minimize damagecaused by heat when the outer resin layer 16 is extruded to cover theouter peripheral surface of the liner.

(Outer Tube)

An outer tube 14 (may also be referred to as an “outer”) includes theouter resin layer 16 (outer resin) covering the outer periphery of theinner tube 12, and the two metal wires 18 buried in parallel with theaxial direction of the inner tube 12 and at equal intervals in thecircumferential direction of the inner tube 12 in the outer resin layer16.

—Outer Resin Layer—

The resin included in the outer resin layer 16 may be a crystallineresin or an amorphous resin. Preferably, the resin has a storage elasticmodulus according to dynamic viscoelasticity of not more than 3,000 MPabecause such a resin is easy to bend. The resin having a storage elasticmodulus of not more than 1,500 MPa is particularly preferable becausesuch a resin is easier to bend.

In the present embodiment, the storage elastic modulus is a valuemeasured at 25° C. among values measured by a dynamic viscoelasticitymeasuring device in a tension mode at 1 Hz frequency and a temperatureincreasing speed of 2° C./minute.

A melting point or a glass transition point (Tg) of the resin includedin the outer resin layer 16 is preferably not more than 210° C., andmore preferably not more than 180° C.

If the resin having the melting point or the glass transition point (inthe case of the amorphous resin) of not more than 210° C., the liner 12is unlikely to be damaged when the resin is extruded into the outerperipheral surface of the liner 12 to cover the liner 12.

A difference between the melting point (T1) of the crystalline resinforming the liner 12 and the melting point or the glass transition point(T2) of the resin forming the outer resin layer 16, i.e., ΔT=(T1−T2), ispreferably in a range of from −50 to +130° C. The manufacture is easieras ΔT becomes larger in the positive range.

Examples of resins that can be applied to form the outer resin layer 16include soft vinyl chloride, a polyethylene-based resin, apolypropylene-based resin, polyoxymethylene, thermoplastic elastomers,such as a styrene-based thermoplastic elastomer, an urethane-basedthermoplastic elastomer, an ester-based thermoplastic elastomer, and apolyethylene-based thermoplastic elastomer, or an olefin-basedthermoplastic elastomer in which EPDM (ethylene-propylene-diene rubber)or ethylene propylene copolymer is dispersed may also be used.

Examples of polyethylene-based resins include high density polyethylene,linear chain low density polyethylene, and low density polyethylene. Themost preferable resin is high density polyethylene. High densitypolyethylene has a density of from 0.941 to 0.970 and is a resin withhigh crystallinity among polyethylenes, and thus has excellent heatresistance and chemical resistance.

Examples of the polypropylene-based resins include a block or randomcopolymer polypropylene, in addition to a homo polypropylene.

Among these resins, the soft vinyl chloride or the thermoplasticelastomer is preferable, as such resins are soft and thus routingproperties may be improved by using the resin.

When a crystalline resin such as a polyethylene-based resin, apolypropylene-based resin, or polyoxymethylene is used as the outerresin layer 16, the outer resin layer 16 fits closely (bonds tightly) tothe inner tube 12, as the outer resin layer 16 has a large moldshrinkage factor. As a result, slipping movement between the inner tube12 and the outer tube 14 (outer resin layer 16) is restricted even whenthe inner tube 12 and the outer resin layer 16 are not bonded with eachother.

The inner tube 12 and the outer tube 14 can be strongly bonded with eachother by easy adhesion treatment, which is described below, such asplasma irradiation or primer treatment, on the outer peripheral surfaceof the inner tube 12, regardless of the material of the outer resinlayer 16.

The thickness of the outer resin layer 16 is preferably from 0.2 to 2.0mm, and more preferably from 0.3 to 1.5 mm, from the viewpoint of thestrength of the control cable, and in view of the relationship to thediameter of the metal wire 18 and to thermal damage to the liner 12.

—Metal Wire—

Two metal wires 18 are buried in the outer resin layer 16 in parallelwith the axial direction of the inner tube 12 and at equal intervals inthe circumferential direction of the inner tube 12.

Examples of the metal wires 18 buried in the outer resin layer 16 mayinclude a hard steel wire, a soft steel wire, a stainless steel wire,and the like. A diameter of the metal wire 18 is preferably from about0.1 to 0.5 mm.

A stranded wire made by stranding one to five metal wires having a wirediameter of from 0.05 to 0.2 mm may preferably be used since theflexibility of an obtained outer casing 10 is increased.

The metal wire 18 may be provided with irregularities intermittently inthe longitudinal direction of the metal wire 18. In this case, theirregularities would enter the resin of the outer resin layer 16 tosuppress the slipping movement of the metal wire 18. As a result,protrusion of the metal wire 18 is effectively suppressed when the outercasing or the control cable is bent.

Such irregularities can be formed, for example, by roll pressing of themetal wire 18.

The metal wire 18 and the resin become a kind of metal fiber reinforcingresin, such that the thermal expansion is halved compared to a case inwhich the metal wires 18 are not buried, and the compression strengthand the tensile strength, particularly at high temperature, are greatlyimproved.

When the outer resin layer 16 is made of a soft resin, such as softvinyl chloride or a thermoplastic elastomer, the resin enters theirregularities of the metal wire 18 only weakly, and the metal wire 18easily protrudes from end terminals of the outer resin layer 16 bybending. If the resin is shifted from the metal wire 18, a reinforcingeffect by the metal wire 18 is easily decreased.

To treat this, the metal wire 18 may be subjected to easy adhesiontreatment to increase adhesiveness with the resin and restrict theslipping movement of the metal wire 18. The easy adhesion treatment isvery effective when the soft resin is used as the outer resin layer 16,but is also effective when the hard resin is used. The effect of theeasy adhesion treatment may increase further by increasing a surfacearea of the metal wires 18, such as by providing the irregularities inthe metal wires 18, using the stranded wire, or the like.

The outer casing 10 shown in FIG. 1 includes two metal wires 18 buriedin the outer resin layer 16 in parallel along the axial direction of theinner tube 12 and at positions symmetrical about the axis, but the metalwires 18 are not limited to two metal wires. For example, as shown inFIG. 2, the control cable 20 may include the three metal wires 18 buriedin parallel with the axial direction of the inner tube 12 and at equalintervals in the circumferential direction of the inner tube 12. Thenumber of the metal wires is preferably three or less, because itbecomes difficult to bend the metal wires as the number of the metalwires increases.

In the present embodiment, “in parallel with the axial direction of theinner tube” in regard to the metal wires 18 does not mean that when theouter casing is configured linearly, an angle between the metal wires 18is limited to 0 degrees, and the angle may change intermittently within10 degrees. In addition, “at equal intervals in the circumferentialdirection of the inner tube” does not mean that the intervals of theplural metal wires 18 buried in the outer resin layer 16 in thecircumferential direction of the inner tube 12 are limited to be exactlyequal, and the intervals may be different from each other by 10%.

<Method of Manufacturing Outer Casing for Control Cable>

A method of manufacturing the outer casing 10 according to the presentembodiment is not particularly limited. For example, the inner tube 12made of the crystalline resin may be inserted inside the outer tube 14with the plural metal wires 18 buried in the outer resin layer 16. Incontrast, it is preferable that, after the inner tube 12 is formed, theouter resin layer 16 is extruded and molded on the outer periphery ofthe inner tube 12, so as to cover the inner tube 12 with the outer tube14 in which the plural metal wires 18 are buried in the outer resinlayer 16 in parallel with and at equal intervals with each other.

Namely, the outer casing according to the embodiment can be manufacturedpreferably by inserting, into a die of an extrusion forming machine, theinner tube including the crystalline resin and the plural metal wires inparallel with the axial direction of the inner tube and at equalintervals in the circumferential direction of the inner tube and byextruding a resin around the outer periphery of the inner tube whilefeeding out the inner tube and the plural metal wires from the die toform the outer tube including the outer resin layer and the plural metalwires buried in the outer resin layer.

FIG. 3 schematically shows a part of the manufacturing steps of thecontrol cable according to the present embodiment. For example, theresin liner 12 may be manufactured in advance, or two extruders areprovided such that one extruder is used to manufacture the resin liner12, and two metal wires 18 and the liner 12 are inserted into the otherextruder from an insertion hole 32 of a nozzle 30 located behind the die34 of the extruder. At this time, the two metal wires 18 are inserted inparallel with the axial direction of the liner 12 and at equal intervalsin the circumferential direction (i.e., symmetrical about the axis) ofthe liner 12. The resin liner 12 and the metal wires 18 are introducedinto the die 34, and a resin tube (outer resin layer 16) is extruded tocover the outer peripheral surface of the liner 12 while being fed fromthe die 34. Thus, the two metal wires 18 are buried in the thickness ofthe resin tube 16 in parallel with the longitudinal direction of theresin tube 16 and at positions approximately symmetrical with eachother.

The resin tube covered as the outer resin layer 16 (outer resin) aroundthe outer peripheral surface of the resin liner 12 has a favorabledimensional accuracy of inner and outer diameters, and does not need tobe passed through an outer diameter adjusting apparatus provided with avacuum apparatus (a former: an apparatus for controlling the outerdiameter by suctioning the outer surface of an extruded tubular body).

When the outer casing 10 according to the embodiment is manufactured asdescribed above, it is preferable to treat at least one contact surfaceof a contact surface between the inner tube (liner) 12 and the outerresin layer 16, or a contact surface between the metal wires 18 and theouter resin layer 16, with the easy adhesion treatment.

The easy adhesion treatment in the invention may be oxidation treatment,such as corona discharge or plasma irradiation, or primer treatment.

If, for example, the liner is made of high density polyethylene orpolyoxymethylene that has poor adhesiveness with the soft vinyl chlorideand the outer peripheral surface of the liner is covered by the softvinyl chloride, the outer resin layer is not adhered to the liner.However, if the outer peripheral surface of the liner is subjected tothe corona discharge or the plasma treatment, adhesiveness between thesoft vinyl chloride and the liner significantly increases, whereby theinner tube 12 and outer tube 14 become integrated, and a highadhesiveness is kept against compression.

Adhesiveness of the metal wires and the resin is usually low. Forexample, if a polypropylene-based elastomer is used for the outer resinlayer 16, an obtained outer casing has an excellent flexibility, but themetal wires 18 may slip in the outer resin layer 16 due to repeatedbending and thus the metal wires 18 may protrude from the outer resinlayer 16.

However, by applying primer to the surface of the metal wires 18,adhesiveness between the resin and the metal greatly increases andprotrusion of the metal wires 18 can be prevented effectively regardlessof bending.

Exemplary types of the primer include: a resin solution (MAO) ofpolyolefin treated with polar group, such as maleic anhydride, acopolymer of an epoxy group-containing monomer, such as glycidylacrylate (GMP), chlorinated polyolefin (CPE), chlorinated ethylene-vinylacetate copolymer (CEVA), and further aqueous or solvent dispersion ofolefin resin particles (PO emulsion). These primers can improveadhesiveness between resin and metal, or between different types ofresins. It is more effective to use the primer with plasma irradiationor corona discharge.

In a conventional method of manufacturing a single-layer outer casingthat has generally been used, the metal wire is introduced into theextruding die and buried in a resin tube, and the inner and outerdiameters are adjusted and determined simultaneously. Such a method,however, involves complicated operations and requires a long time, andeventually discharges a large amount of resin and metal waste materials.Further, such an outer casing becomes elliptical because diameters aredifferent between a portion where the metal wire is present and aportion where the metal wire is not present. It is necessary, therefore,to make the inner diameter relatively large. Otherwise the loadefficiency may be deteriorated.

In contrast, in the two-layered outer casing of the embodiment, it isnot necessary to control the inner diameter, which is the most importantportion for the outer casing, with high accuracy in order to cover theouter periphery of the liner made of crystalline resin made in advanceor previously into a tubular shape with resin.

In the conventional single-layer outer casing, the resin was selected byconsidering sliding ability, and a hard resin was usually selected. As aresult of this, the routing properties had to be sacrificed. However, inthe outer casing having the two-layered structure of the invention,since it is possible to select the liner by considering the slidingability, and select the outer resin layer by considering the routingproperties, a well-balanced outer casing can be provided.

The outer periphery of the outer casing having the two-layered structureof the invention may be covered by a cylindrical protector or foamedbody for purposes such as oil proofing, heat resistance, vibrationproofing, and hammering noise prevention.

<Control Cable>

The control cable of the invention includes the outer casing accordingto the invention as described above and an inner cable inserted into theouter casing (inner tube).

A metal wire may be used as an inner cable, and should be selected inaccordance with the required strength or the like.

The metal wire may be coated with resin, such as nylon, for therustproof purpose.

Grease may be injected into an insertion hole of the outer casing toimprove the slidability.

The control cable of the invention is not limited to a specific use, andmay be used in various uses, such as a sunroof open/close cable, a seatcable, a window open/close cable, a parking break cable, a trunk openingcable, a fuel opening cable, a bonnet cable, a key lock cable, a heateradjusting cable, an automatic transmission cable, an a throttle cable,or an accelerator cable.

EXAMPLES

Examples of the invention will be described below, but the invention isnot limited to such examples.

First, materials and treatment details used in the examples andcomparative examples are described below.

The storage elastic modulus listed in used resins was measured by usinga dynamic viscoelasticity measuring device (manufactured by TAInstruments) at a temperature increasing speed of 2° C./minute and afrequency of 1 hz in a tension mode.

(Resin)

Resin PE: HI-ZEX 500H (high density polyethylene, MFR: 0.10, density:0.958, storage elastic modulus: 1300 MPa, melting point: 132° C.,manufactured by PRIME POLYMER).

Resin POM: Iupital F10 (polyoxymethylene, density: 1.41, storage elasticmodulus: 2800 MPa, melting point: 160° C., manufactured by MitsubishiEngineering-Plastics Corporation).

Resin PBT: NOVADURAN 5010Trxa (polybutylene terephthalate, density:1.27, storage elastic modulus: 2400 MPa, melting point: 220° C.,manufactured by Mitsubishi Engineering-Plastics Corporation).

Resin PC: Iupilon E2000 (polycarbonate (amorphous resin)), density:1.20, storage elastic modulus: 2300 MPa, glass transition point: 150°C., manufactured by Mitsubishi Engineering-Plastics Corporation).

Resin TPO: MILASTOMER M4400B (polypropylene-based thermoplasticelastomer resin, MFR: not more than 1, density: 0.89, storage elasticmodulus: 410 MPa, melting point: 150° C., manufactured by MitsuiChemicals, Inc.).

Resin PP: Prime Polypro E105GM (MFR: 0.5, density: 0.89, storage elasticmodulus: 960 MPa, melting point: 162° C., manufactured by PRIMEPOLYMER).

Resin PVC1: VINIKA CE85E (soft vinyl chloride (amorphous resin), Ahardness: 83, density: 1.44, glass transition point: 22° C.,manufactured by Mitsubishi Chemical Corporation).

Resin PVC2: VINIKA T-620 (hard vinyl chloride (amorphous resin), Dhardness: 90, density: 1.41, glass transition point: 100° C.,manufactured by Mitsubishi Chemical Corporation).

LLDPE: linear low density polyethylene, SUMICASEN E FV102 (MFR: 0.8,density: 0.926, melting point: 125° C., storage elastic modulus: 440MPa, manufactured by Sumitomo Chemical Co., Ltd.).

LDPE: low density polyethylene, Sumikathene F218-0 (MFR: 1.0, density:0.919, melting point: 109° C., storage elastic modulus: 115 MPa,manufactured by Sumitomo Chemical Co. Ltd.).

(Metal Wire)

Hard steel wire: a heat-treated metal wire having a diameter of 0.33 mm.

Stranded wire: a metal wire stranded by three hard steel wires eachhaving a diameter of 0.15 mm at 2 mm pitch.

(Easy Adhesion Treatment)

Plasma irradiation: A material (resin liner) was subject to plasmairradiation at a speed of 100 mm per second by the Real Plasma APG-500manufactured by KASUGA ELECTRIC WORKS LTD.

Primer: The metal wire was immersed in UNISTOLE R300 (organic solventsolution of acid-modified polypropylene manufactured by Mitsui ChemicalsInc.) for 0.5 minute and dried at 150° C. for two minutes before use.

Example 1 (Manufacture of Resin Liner)

Pellets of the resin PE were fed into a single-screw extruder(manufactured by SOKEN) having a screw diameter of 30 mm, alength-diameter ratio (L/D)=22 to sequentially extrude tubular moldedproducts each having 2.0 mm inner diameter and 2.8 mm outer diameter ata screw temperature of 200° C. Immediately after the extrusion, theouter diameter was adjusted by a former to obtain a resin liner (innertube).

(Manufacture of Two-layered Outer Casing)

The resin liner previously manufactured as described above was insertedinto a cross-head type single-screw extruder (manufactured by the JapanSteel Works, Ltd.), which has a screw diameter of 30 mm and the ratio oflength to diameter (L/D)=30, from the rear part of the die.

Meanwhile, pellets of the resin PP were fed to the single-screwextruder, and while the outer periphery of the resin liner was coveredby the resin PP at a screw temperature of 210° C. to form the outerresin layer, two hard steel wires were introduced into the die, and thenmolded by extrusion in such a manner that the two hard steel wires wereburied in the longitudinal direction and in parallel and symmetricalpositions in the middle portion of the thickness of the outer resinlayer (distance between the metal wires is 3.5 mm). As a result of this,an outer casing having a two-layered structure and an outer diameter of5 mm was obtained.

[Evaluation]

An inner cable (SWRH62A manufactured by UNIFLEX CO., LTD., diameter: 1.5mm) was inserted into the obtained outer casing to produce a controlcable.

The outer casing and the control cable were evaluated as describedbelow.

(Stroke Loss)

FIG. 4 is a schematic view for explaining how stroke loss is measured. Acontrol cable 40 having a length of 1.5 m was routed in a reverseS-shape having a diameter of 200 mm, as shown in FIG. 4. Metal fittings24 fitted to both ends of the outer casing were fixed, and one end ofthe inner cable 22 was fixed to the fitting member 50. In this state,the other end of the inner cable 22 was held by a tensile testingmachine 60, and pulled in the direction of arrow A at 80° C. and with aforce of 98 N, and the “tensile length” of the inner cable was measuredby a displacement gauge 70 to obtain a stroke loss value.

Meanwhile, a conventional flat-steel-wire winding type control cable wasmanufactured for measurement, and the obtained stroke loss value was 3.1mm.

(Load Efficiency)

FIG. 5 is a schematic view for explaining how load efficiency ismeasured. A control cable having a length of 1.5 m was routed in an Rshape having a diameter of 200 mm, and the metal fittings 24 fitted toboth ends of the outer casing were fixed. A load meter 80 was attachedto one terminal end of the inner cable 22, and the other terminal end ofthe inner cable 22 was pulled with a force of 98 N at room temperatureby the tensile testing machine 60 to measure a load transmitted to theterminal end side. As a result of this, load efficiency was obtained. Itis determined that when this ratio increases, the efficiency becomeshigher.

(Variation of Inner Diameter)

The inner diameter of outer casing having a length of 3,000 mm wasmeasured by a micrometer at intervals of 500 mm, whereby a differencebetween the maximum portion and the minimum portion was obtained.

(Thermal Expansion)

After an outer casing having a length of 1,000 mm was left for threehours in an 80° C. atmosphere, a length (L1) was obtained. A differenceL1-L0 between the length (L1) and a length (L0) measured at roomtemperature was measured.

(Routing Properties)

A control cable having a length of 150 mm was fixed at both ends suchthat the metal wires extended horizontally, and a load (N) was measuredwhen one end of the control cable was bent vertically at a right angleto the longitudinal direction. As this value decreases, the routingproperties are improved.

(Protrusion of Metal Wire)

After a control cable having a length of 150 mm was bent at R50, aprotruded measurement of the metal wire at the terminal end of the outercasing was measured.

Examples 2 to 7

The outer casing and the control cable were manufactured and evaluatedin the same manner as in Example 1 except that the materials andmanufacturing conditions listed in Table 1 below replace those ofExample 1.

TABLE 1 EXAMPLE 1 EXAMPLE 2 EXAMPLE 3 EXAMPLE 4 EXAMPLE 5 EXAMPLE 6EXAMPLE 7 Type of metal wire Hard steel wire Hard steel wire Hard steelwire Hard steel wire Hard steel wire Hard steel wire Stranded wire LinerType PE PE PE PE PE PE PE Resin Melting point or 132 132 132 132 132 132132 Tg (° C.) Outer Type PP PP TPO TPO PVC1 POM TPO Resin Melting pointor 162 162 150 150 22 160 150 Tg (° C.) Temperature −30 −30 −18 −18 110−28 −18 difference ΔT (° C.) Easy adhesion treatment — Primer to metal —Primer to metal Primer to metal — Primer to metal wire wire wire wirePrasma irradiation to PE Use or non-use of former Not used Not used Notused Not used Not used Not used Not used (during molding of outer)Evaluation item Moldability Good Good Good Good Good Good Good Variationof inner <10 <10 <10 <10 <10 <10 <10 diameter (mm) Thermal expansion(mm) 1.9 1.8 1.9 1.8 1.7 1.8 1.9 Routing properties (N) 7.2 7.2 4.9 5.04.8 8.2 3.2 Stroke loss (mm) 4.0 3.8 4.1 4.0 4.0 3.5 5.6 Load efficiency(%) 63.4 63.4 63.4 63.4 63.4 63.4 63.4 Protrusion of metal 1 0 2 0 0 1 0wire (mm) Weight (g/m) 16.7 16.7 16.6 16.6 24.0 23.6 16.6

Comparative Examples 1 to 3-3

The outer casing and the control cable were manufactured and evaluatedin the same manner as in Example 1 except that the materials andmanufacturing conditions listed in Table 2 below replace those ofExample 1.

TABLE 2 COMPARATIVE COMPARATIVE COMPARATIVE COMPARATIVE COMPARATIVECOMPARATIVE EXAMPLE 1 EXAMPLE 2-1 EXAMPLE 2-2 EXAMPLE 3-1 EXAMPLE 3-2EXAMPLE 3-3 Type of metal wire Hard steel wire — Hard steel wire — Hardsteel wire — Liner Type — PC PC PVC2 PVC2 PVC2 resin Melting point — 150150 100 100 100 or Tg (° C.) Outer Type PP — PP — PE PE resin Meltingpoint 162 — 162 — 132 132 or Tg (° C.) Temperature — — −12 — −32 −32difference T (° C.) Easy adhesion treatment — — — — — — Use or non-useof former Used — Not used — Not used Not used (during molding of outer)Evaluation item Moldability Adjustment: large, Liner molding DefectiveLiner molding Defective Shrunk in wasted amount: failed (did notdimensions failed (did not dimensions longitudinal large pass throughthe pass through the direction, former) former) Deformed as inner andouter diameters are larger than 300 μm Variation of inner 80 — Large(about 80) Large (about 105) Large (about 200) diameter (μm) Thermalexpansion (mm) 1.8 — 1.7 — 2.1 9.5 Routing properties (N) 7.8 — 10.2 —7.5 3.0 Stroke loss (mm) 4.3 — 4.0 — 6.3 40 Load efficiency (%) 51.5 —21.2 — 20.3 20.5 Protrusion of metal 1 — 1 — 2 — wire (mm) Weight (g/m)16.5 — 18.2 — 18.7 17.0

Examples 8 to 10, Comparative Examples 4 to 6

The outer casing and the control cable were manufactured and evaluatedin the same manner as in Example 1 except that the materials andmanufacturing conditions listed in Table 3 below replace those ofExample 1.

TABLE 3 COMPARATIVE COMPARATIVE COMPARATIVE EXAMPLE 8 EXAMPLE 9 EXAMPLE10 EXAMPLE 4 EXAMPLE 5 EXAMPLE 6 Type of metal wire Stranded wire Hardsteel wire Hard steel wire Hard steel wire — Flat steel wire windingLiner Type PBT LLDPE LDPE — PE PE resin Melting point or Tg 220 125 109— 132 132 (° C.) Outer TYPE TPO PP PP TPO PP PP resin Melting point orTg 150 162 162 150 162 162 (° C.) Temperature 70 −37 −53 — −30 −30difference ΔT (° C.) Easy adhesion treatment Primer to metal — — — — —wire Use or non-use of former Not used Not used Not used Used Not usedNot used (during molding of outer) Evaluation item Moldability Good GoodLiner softened Could not control Good Good Measurements measurementsvaried Variation of inner <10 20 40 — <10 <10 diameter (μm) Thermalexpansion (mm) 1.7 2.0 2.2 — 8.2 1.8 Routing properties (N) 3.6 7.0 6.8— 4.0 6.5 Stroke loss (mm) 4.0 4.1 4.5 — 30 3.1 Load efficiency (%) 65.254.3 48.5 — 63.4 63.4 Protrusion of metal 0 1 1 — — — wire (mm) Weight(g/m) 17.6 16.6 16.5 — 15.0 59.7 Remarks Unfavorable thermal expansionand stroke loss

Molding of the liner was attempted using polycarbonate (PC: amorphousresin) and a hard vinyl chloride (PVC2: amorphous resin). The moldingwas failed, because the materials were discharged from the die of theextruder, but were not able to pass through an outer diameter adjustingapparatus (former: an apparatus for controlling the outer diameter bysucking the outer surface of an extruded tubular body) (ComparativeExamples 2-1, 3-1).

The reason for this was considered to be that the resistance increasedwhen the amorphous resin passed through the former, as the amorphousresin had a high coefficient of friction (for reference, the coefficientof static friction for steel: PE/0.11, PVC/0.22, and PC/0.36).

Meanwhile, the liner was molded from each of the above-mentioned twotypes of resins without using the former, but the obtained inner andouter diameter measurements were very poor.

It was attempted that a liner having a poor inner and outer diametermeasurement was used and covered by the outer resin. This resulted inincreasing the variation of measurements of the liner (ComparativeExamples 2-2, 3-2).

A reason for the increased variation of measurements was considered tobe that, in addition to the absence of the former to control the outerdiameter, the liner resin was heated above the glass transition pointand become a rubber-like state, when the amorphous resin liner touched amelted resin at nearly 200° C., whereby the deformation of the liner wasfacilitated.

This does not happen when the crystalline resin is used as the liner.The reason for this is not apparent but, presumably, in the case of thecrystalline resin, since a latent heat of melting of crystal is high,the crystalline resin is cooled before melting of crystal occurs andbecome solid, such that the deformation can be prevented.

Comparative Example 5 is an example of a two-layered tube in which themetal wires were not buried. Because of the absence of the metal wires,thermal expansion and stroke loss were significantly deteriorated.

Comparative Example 6 is an example of a conventional flat steel wirewinding product. It is apparent that the weight of the product is 59.7g/m, i.e., very heavy.

The disclosure of Japanese Patent Application No. 2013-167075 isincorporated herein by reference in its entirety.

All publications, patents, patent applications, and technical standardsmentioned in this description are incorporated herein by reference tothe same extent as if each individual publication, patents, patentapplication, or technical standard was specifically and individuallyindicated to be incorporated by reference.

1. An outer casing for a control cable, the outer casing comprising: aninner tube, which includes a crystalline resin; and an outer tube, whichincludes an outer resin layer covering an outer periphery of the innertube and, in the outer resin layer, includes a plurality of metal wiresburied in parallel with an axial direction of the inner tube and atequal intervals in a circumferential direction of the inner tube,wherein a surface of the metal wires has been subjected to primertreatment.
 2. The outer casing for a control cable according to claim 1,wherein the crystalline resin included in the inner tube has a meltingpoint of 120° C. or higher.
 3. The outer casing for a control cableaccording to claim 1, wherein a resin included in the outer resin layeris a thermoplastic elastomer or a soft vinyl chloride resin.
 4. Theouter casing for a control cable according to claim 1, wherein a contactsurface between the inner tube and the outer resin layer has beensubjected to easy adhesion treatment.
 5. A method of manufacturing anouter casing for a control cable, the method comprising: forming anouter tube including an outer resin layer and a plurality of metal wiresburied in the outer resin layer by inserting, into a die of an extrusionforming machine, an inner tube including a crystalline resin, togetherwith the plurality of metal wires in parallel with an axial direction ofthe inner tube and at equal intervals in a circumferential direction ofthe inner tube, and by extruding a resin around an outer periphery ofthe inner tube while feeding out the inner tube and the plurality ofmetal wires from the die.
 6. A control cable comprising the outer casingfor a control cable according to claim 1, and an inner cable insertedinto the outer casing for a control cable.
 7. The outer casing for acontrol cable according to claim 2, wherein a resin included in theouter resin layer is a thermoplastic elastomer or a soft vinyl chlorideresin.
 8. The outer casing for a control cable according to claim 2,wherein the crystalline resin included in the inner tube has a meltingpoint of 265° C. or lower.
 9. The outer casing for a control cableaccording to claim 4, wherein the easy adhesion treatment is coronadischarge treatment, plasma irradiation treatment, or primer treatment.10. A control cable comprising the outer casing for a control cableaccording to claim 2, and an inner cable inserted into the outer casingfor a control cable.
 11. A control cable comprising the outer casing fora control cable according to claim 3, and an inner cable inserted intothe outer casing for a control cable.
 12. A control cable comprising theouter casing for a control cable according to claim 7, and an innercable inserted into the outer casing for a control cable.
 13. The methodof manufacturing an outer casing for a control cable according to claim5, further comprising subjecting a surface of the metal wires to primertreatment before the forming of the outer tube.